Oven appliances frequently include a window for the user to view the contents of the oven during cooking Allowing the user to view food without opening the door is convenient and avoids the escape of heat, steam, and fumes that occurs by opening the door. Viewing the food allows the user to check on e.g., cooking progress and browning. One or more lights in the oven cavity may also be provided to assist with viewing.
To allow for the window, an opening is created in the oven door. To prevent the escape of heat, the window includes one more pieces of glass or other transparent material through which the user can view the oven cavity. The glass may be treated for easier cleaning and exposure to the temperatures of oven use and may also include other features for oven application. If, for example, the oven is a microwave or includes microwave features, the window may include a layer of mesh to assist with shielding. Different types of glass can be used to provide the oven window.
During cooking operations, the oven is operated at temperatures that may exceed 450° F. For oven self-cleaning cycles, even higher temperatures may be obtained. Insulation is typically provided around the oven to insulate the user and the environment from these temperatures. For the oven window, several layers of glass may be used in order to provide insulation between the oven cavity and the exterior of the appliance while still allowing viewing through the window.
Like many other materials, glass will grow as its temperature is raised by heating. For example, plate glass can have a linear thermal expansion coefficient of about 5.0×10-6 in/in ° F. As such, the glass installed in an oven window, particularly glass that is exposed directly to the heat of the oven cavity, can expand significantly along both lateral and longitudinal directions as its temperature is increased.
Such thermal expansion presents certain challenges in the design and manufacture of an oven appliance. Where a window contacts or attaches to an oven door, consideration must be given to the relative movement of the glass that will occur due to the thermal expansion. Restraint of such movement during heating can lead to e.g., glass damage such as cracking or shattering.
Previous approaches to positioning the window while allowing for thermal expansion are varied. For example, adhesives or gaskets have been applied in various configurations as well as special mounting procedures when fasteners are used that extend through the glass. Combinations of these approaches have also been applied.
Accordingly, an oven appliance that allows for the thermal expansion of a window used for viewing the oven cavity would be useful. More particularly, an oven appliance that can allow the glass window to expand along both its lateral and longitudinal directions without causing damage to the glass would be beneficial. Such an oven that can allow for such expansion without the use of special adhesives or gaskets would also be very useful.